Common: Add a helper function to generate a 8.3 filename from a long one.

Core: Fix the SDMC Directory implementation to make blargSnes work.

src/common/file_util.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <array>
 #include <fstream>
 #include <cstdio>
 #include <cstring>
@@ -131,6 +132,16 @@ std::string &GetExeDirectory();
 size_t WriteStringToFile(bool text_file, const std::string &str, const char *filename);
 size_t ReadFileToString(bool text_file, const char *filename, std::string &str);
 
+/**
+ * Splits the filename into 8.3 format
+ * Loosely implemented following https://en.wikipedia.org/wiki/8.3_filename
+ * @param filename The normal filename to use
+ * @param short_name A 9-char array in which the short name will be written
+ * @param extension A 4-char array in which the extension will be written
+ */
+void SplitFilename83(const std::string& filename, std::array<char, 9>& short_name,
+                     std::array<char, 4>& extension);
+
 // simple wrapper for cstdlib file functions to
 // hopefully will make error checking easier
 // and make forgetting an fclose() harder